[Regulatory effect of diammonium glycyrrhizinate on Th1/Th2 deviation in bronchial asthma: experiment with rats].

Objective: To study the regulatory effect of diammonium glycyrrhizinate (GL) on the Th1/Th2 deviation in bronchial asthma.

Methods: Thirty Wistar rats were injected intraperitoneally with antigen solution including ovalbumin (OVA), inactivated pertussis vaccine, and aluminum hydroxide for the purpose of sensitization. Fourteen days later OVA was sprayed 20 min everyday for a consecutive 5 days to evoke sensitization, thus models of asthma were established. Then the 30 rats were randomly divided into 3 equal groups: asthma model group, model+GL group, and model+DXM group. Another 10 rats were used as control group. All rats underwent tracheal intubation to perform the breathing curves. By the end of the experiment the rats were killed with their lungs taken out to undergo pathological examination. Suspension of splenocytes was prepared, the level of interferon (IFN)-gamma, a cytokine mainly secreted by Th1 cells, was detected by L929-VSV system, and the IL-4 level was detected by ELISA.

Results: The amplitude of the breathing curve of the GL group was similar to that of the DXM group, both significantly lower than that of the model group [(0.139+/-0.011) mV, both P<0.01] and higher than that of the control group. The respiratory rates of all groups became faster than normal. Pathology showed infiltration of inflammatory cells and proliferation of cup-shaped cells in the pneumonic tissues in the model group, and such damages were much slighter in the GL and DXM groups. The IFN-gamma level of the model group was (1.6+/-0.4) U, significantly lower than that of the control group [(3.7+/-1.0) U, P<0.05]. The IFN-gamma level of the GL group was (18.7+/-5.5) U, significantly higher than those of the DXM group [(2.1+/-0.3) U], model group and control group (all P<0.01). The IL-4 level of the model group was (305+/-36) pg, significantly higher than those of the GL group [(168+/-10) pg, P<0.01], DXM group [(213+/-47) pg], and control group [(54+/-6) pg, P<0.01], however, there was no significant difference between the GL and DXM groups.

Conclusion: GL increases the IFN-gamma level and decreases the IL-4 level, thus promoting the polarization of Th1 cells, regulating the Th1/Th2 deviation, and alleviating asthma.